An electric motors is a device that converts electrical energy into mechanical energy under the principle of electromagnetic induction and can be broadly classified into direct current motors and alternating current motors, depending on the type of the input power.
PMDC motors are a type of direct current motor which has a magnetic field generated by a permanent magnet. PMDC motors are widely used in various fields, including portable electronic devices and in vehicle accessories.
Different application fields impose different requirements on the performance of the motor. For example, in a vehicle heating, ventilation and air conditioning (HVAC) system, a PMDC motor is used to introduce fresh air into the car and is required to produce low noise. FIG. 1 illustrates a known PMDC motor used in the car HVAC system. The motor includes a housing 100, a stator magnet fixed to an inner surface of the housing 100, and a rotor core 300 disposed in an interior of the stator magnet 200. In this motor, the thickness of the stator magnet 200 is relatively small, and the outer diameter of the rotor core 300 is relatively large. In this particular example, it is 17.9 mm. As a result, the rotor core 300 has a large rotational inertia, which can easily produce noise and thus does not satisfy the consumers' low noise requirement for use in a vehicle HVAC system.
Accordingly, there is a desire for an improved low noise PMDC motor, suitable for use in a vehicle HVAC system.